Key Points•Boeing aiming to double the range of its Harpoon missile •Harpoon Next Generation will consist of a fuel-efficient engine, additional fuel, and a 300-pound class warhead

Boeing is developing a kit to upgrade existing Harpoon Block II missiles for extended range, in the hope of attracting interest from the US Navy's (USN's) new frigate programme, officials announced on 14 April.

Called Harpoon Next Generation, the new version would include a more fuel-efficient engine, additional fuel, and a smaller 300-pound class warhead, company officials told reporters at the Navy League Sea-Air-Space symposium in National Harbor, Maryland.

"We're looking at doubling the range of Harpoon from 67 nm to 134 nm," said Jim Brooks, director of cruise missile systems weapons programmes for Boeing Global Strike Weapons and Missile Systems, a division of Boeing Defense, Space and Security.

Existing customers, such as the USN and 27 international partners, would be able to upgrade their Harpoon Block II inventory with the kit, which could be supplied to a customer's depot for installation, or the customer could opt to have the kit installed by Boeing.

So far, the company has delivered 7,500 Harpoon Block II missiles, and the USN's Naval Air Systems Command (NAVSEA) let a contract to Boeing in 2013 for the production of 40 Block IIs.

According to USN data, the unit cost for a Harpoon Block II is USD1.2 million. Boeing officials said the cost to upgrade to the Harpoon Next Generation is competitive, and that customers can choose to retrofit their existing inventory or opt for the new missiles to be built from scratch.

"A new Next Gen would be approximately the same [cost] as for one of our Harpoons," said Brooks. "A retrofit would be half the cost of a new missile."

Offering up an extended range capability for Harpoon at an affordable cost has been a driving force behind the upgrade kit, officials said.

"It's really looking at leveraging that installed base of existing Harpoon," said Beth Kluba, vice-president of weapons and missile systems for Boeing Military Aircraft. "That's one of the key affordability tenets we're offering with Harpoon Next Generation."

Officials noted that the Harpoon missile system has proceeded through 10 upgrades over the years, with concerted effort focused on the front end of the missile with improved guidance capabilities, navigation, and seeker capability. Brooks said that while Harpoon Next Generation is considered the next logical upgrade in the missile's evolution, its improvements are focused on the back end of the system; adding more fuel, moving to a more fuel-efficient engine, and bringing in a lighter warhead to compensate for the increased fuel load.

The kit is expected to be ready in 2018, officials said, and the team is working towards a possible demonstration of the improved missile in 2016 for the USN.

A ground test of the back half of the missile in 2014 proved that the kit could double the range of the existing Harpoon, officials added. For the test, the team installed a high-efficiency turbo jet engine in the missile section as well as an expanded fuel capacity system, as a representation of Harpoon Next Generation's full fuel system volume.